AbstractA review on the recent developments in the field of long-wavelength (Lambda >1.2 µm) high-brightness optically-pumped semiconductor disk lasers (OPSDLs) is presented. As thermal effects have such a crucial impact on the laser performance particular emphasis is given to modelling the thermal behaviour and optimisation of the heat-sinking. Selected OPSDL devices, realized in different III-V and IV-VI semiconductor material systems, with corresponding emission wavelengths between 1.2 µm and 5.3 µm are presented. Specific applications in this broad spectral range are addressed and methods to obtain high output power are discussed in terms of the underlying material properties and device operating principles.